Golf balls, whether of solid or wound construction, generally include a core and at least a cover or outer coating. Solid golf balls, as compared with wound balls, provide better distance than wound balls due to their lower driver initial spin. Meanwhile, the wound construction provides a softer “feel” and higher spin rate—characteristics often preferred by accomplished golfers who are able to control the ball's flight and positioning.
The properties of a conventional solid ball may be modified by altering the typical single layer core and single cover layer construction to provide a ball having at least one intermediate layer disposed between the cover and the core. The core may be solid or fluid-filled, and may be formed of a single layer or one or more layers. Covers, in addition to cores, may also be formed of one or more layers. These multi-layer cores and covers are sometimes known as “dual core” and “dual cover” golf balls, respectively. One piece golf balls are also available. The difference in play characteristics resulting from these different types of constructions can be quite significant. The playing characteristics of multi-layer balls, such as spin and compression, can be tailored by varying the properties of one or more of the core, intermediate and/or cover layers.
By altering solid golf ball construction and composition, manufacturers can vary a wide range of playing characteristics such as resilience, durability, spin, and “feel”, optimizing each according to various playing abilities and achieving a solid golf ball possessing feel characteristics more like their wound predecessors. For example, by shifting the density or mass of the golf ball toward the center of the ball, the moment of inertia of the golf ball can be reduced, thereby changing the spin decay of the ball. In this regard, core is the “engine” of the golf ball when hit with a club head. That is, the core is the golf ball's principal source of resiliency. Meanwhile, the intermediate layers based on ionomers may aid in maintaining initial speed, contribute to desired spin rate, and improve playability/impact durability as well as acting as a moisture barrier to protect the cores from COR loss. The cover, while intended to protect the golf ball from scuffing, may also be modified to target a desired spin rate, feel, and playability, and address such issues as lift and drag.
Accordingly, there is a need for golf balls configured with and incorporating materials in any or all of the core, intermediate layer and/or cover which improve performance, achieve superior golf ball durability, resilience and demonstrate a unique spin profile. In this regard, golf ball manufacturers have found that unique profiles may be achieved in golf balls having property gradients anywhere from the inner core toward the outer cover surface. For example, golf balls having a polyurethane or polyurea outer layer formed about an ionomer resin inner cover layer have been disclosed. Typical golf ball materials include ionomers and acid copolymers due to their durability and desirable performance characteristics such as scuff resistance and rebound. However, adhesion and durability difficulties often arise between layers due to incompatibility of the materials in those layers. Such difficulties increase manufacturing costs and create performance issues which negatively impact the golf ball manufacturer's reputation. Additionally, utilizing multiple layers to accomplish property gradients in a golf ball restricts the possible thickness range for each layer due to manufacturing limitations. Thus, golf ball manufacturers seek to develop golf balls which achieve desired playing characteristics without the aforementioned adhesion problems and layer thickness restrictions/limitations associated with the need to incorporate multiple layers in the golf ball in order to achieve property gradients. The present invention addresses these concerns by providing a golf ball comprising at least one property gradient within a center or at least one layer resulting from at least one treated region within the center and/or layer having been treated with a property-altering organometallic composition.